CODEWITHSUNDEEP
javascriptdata-structures
Alex D.
Alex D.

Reputation: 73

How to store common expenses data in JS

I am new to JS and programming in general. I am writing an expenses calculator for people who pay for each other. The calculator should allow a person to pay for the whole group or just for part of the group or one person. My issue is that i don't know how to store data for each pair of people. Let's say a groups consists of 5 people. Bob payed for Alice $10. Alice payed $50 for Bob, John and herself and John payed $35 for whole group.

What is a better way to store such calculations?

I was thinking to use object but it doesn't seem to suit in this situation

I need a way to store debt for each pair of people in the group so that i can easily modify this information.

Upvotes: 0

Views: 50

Answers (2)

Jonas Wilms
Jonas Wilms

Reputation: 138247

I would just keep an array of transactions:

 const all = Symbol();

 const transactions = [
   { from: "Alice", to: "Bob", amount: 500 },
   { from: "Bob", to: all, amount: 1000 }
 ];

That way, you can easily add new transactions, e.g.

  transactions.push({ from: "Bob", to: "Alice", amount: 500 });

To then get the current balance between two people, you can go over the transactions and sum them up:

  let balance = 0; // from Alice to Bob
  for(const { from, to, amount } of transactions) {
     if(from === "Alice" && (to === "Bob" || to === all))
        balance += amount;
     if(from === "Bob" && (to === "Alice" || to === all))
        balance -= amount;
  }

Upvotes: 1

David Alvarez
David Alvarez

Reputation: 1286

I would use object (if I don't need to save all the transactions):

Assuming it's a group of 3

const Bob = {
    friends: [
        {Alice: 10},
    ],
};

const Alice = {
    friends: [
        {Bob: 50/3},
        {John: 50/3},
    ],
};

const John = {
    friends: [
        {Bob: 35/3},
        {Alice: 35/3},
    ],
};

const groupOfFriends = [Bob, Alice, John];

I think from this data structure you can guess who ows who something.

Upvotes: 1

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